Gasoline Engine Exhaust Profile


IARC Monograph Vol. 46, 1989 (Group 2B)
IARC Monograph Vol. 105, 2014 (Group 2B)

Gasoline Engine Exhaust Profile


  • A complex mixture of gases and particulate matter produced when gasoline fuel combusts
  • Associated cancer: Lung cancer (limited evidence)
  • Most important routes of exposure: Inhalation
  • Primary sources: Cars, power generators, and hand-held equipment (ex. chainsaws) that use gasoline engines
  • Occupational exposures: Approximately 1.5 million Canadians are occupationally exposed to gasoline engine exhaust across many industrial sectors
  • Environmental exposures: Proximity to traffic increases exposure; those walking, cycling, driving, working, living, or attending school on or near major roadways are more likely to be exposed
  • Fast fact: Traffic emissions can infiltrate buildings; for example, vehicle emissions can account for up to half of indoor ultrafine particle mass.

General Information

Gasoline engine exhaust, produced when gasoline fuel combusts, is a complex mixture of gases (e.g. carbon monoxide, nitrogen oxides, and volatile organic compounds) and particulate matter (e.g. elemental and organic carbon, ash, sulfate, and metals).[1] The composition of gasoline engine exhaust depends on a number of factors, including the formulation of the gasoline being burned, mechanical characteristics and age of the engine, vehicle weight and speed, pattern of use, maintenance, and emission control systems.[2,3] Gasoline and diesel engine exhaust contain similar gases and particulate matter but in different proportions. Generally, compared to diesel engines gasoline engines emit more carbon monoxide and hydrocarbons, and less particulate matter, nitrogen oxides, carbon dioxide, and sulfur compounds.[4]

In 2013, the International Agency for Research on Cancer (IARC) classified gasoline engine exhaust as possibly carcinogenic to humans (Group 2B).[2] This classification was based on inadequate evidence of carcinogenicity in humans, a reflection of the difficulty in separating effects of diesel and gasoline exhaust. There was sufficient evidence that the condensates of gasoline engine exhaust can cause lung cancer in experimental animals.[2]

Short-term exposure to gasoline engine exhaust may irritate the eyes, nose, or throat, aggravate existing respiratory allergies, and lead to headache, light-headedness, or tingling extremities.[5] Long-term health effects have been assessed through epidemiological studies examining proximity to road traffic. The associated long-term health effects include increased illnesses related to respiration and aggravated asthma in children, decreased cardiovascular health, and worsened symptoms in those with existing heart and lung conditions.[6]

Regulations and Guidelines

Occupational Exposure Limits (OEL)

There are no occupational exposure limits established at federal or provincial levels for gasoline engine exhaust. However, occupational exposure limits for components of gasoline engine exhaust (such as carbon monoxide or particulate matter) exist within provincial and federal environmental legislation.[7]

Environment Canada Guidelines

The Canadian Environmental Protection Act (CEPA) outlines a number of regulations that influence gasoline engine exhaust emissions. They include:

Regulation Year
Benzene in Gasoline 1997[8]
Contaminated Fuel 1991[9]
Gasoline 1989[10]
On-Road Vehicle & Engine Emission 2002[11]
Off-Road Small Spark Ignition Engine Emission 2003[12]
Marine Spark-Ignition Engine & Off-Road Recreational Vehicle Emission 2011[13]
Sulphur in Gasoline 1998[14]

Gasoline Fuel Use in Canada

Gasoline engines are used in cars, power generators, and hand-held equipment such as chainsaws and leaf blowers.[1]

On average, 60% of gasoline consumption in Canada occurs in Ontario and Quebec, 32% in the western provinces, and 8% in the Atlantic provinces and territories.[15] In 2014, approximately 43.4 billion litres of gasoline were sold for road motor vehicles in Canada.[16]

Regulations regarding fuel composition and emission standards in Canada (aligned with the US Environmental Protection Agency) should result in lower gasoline exhaust emissions across North America.[17] The Sulphur in Gasoline Regulation, for example, requires that sulphur content be lowered gradually to a level of 10 ppm by January 2020.[14] Lower sulphur content in the fuel leads to lower emissions of particulate matter in the exhaust. Furthermore, numerous regulations have been developed – and others are under review – that outline allowable emissions for new models of on- and off-road vehicles and engines.[8,11,12]

In order to reduce harmful exhaust emissions, newer gasoline engines in cars have been fitted with electronic feedback control systems, port fuel injection, and three-way catalyst systems. These are technologies that reduce emissions of particulate matter, nitrogen oxides, carbon monoxide, non-methane hydrocarbons, and unregulated emissions.[1]

Environmental Exposures Overview

Exposure to gasoline engine exhaust in the general population increases with proximity to traffic.[1] In calm conditions, emissions accumulate near roadways; concentrations of carbon monoxide, metals, and particulate matter decline sharply approximately 300 metres from the road.[18] Children who live in homes or go to schools that are located downwind from major highways are more likely to be exposed to gasoline engine exhaust.[1] Traffic emissions can infiltrate buildings; for example, vehicle emissions can constitute 24-47% of indoor ultrafine particle mass.[19] In addition, individuals are more likely to be exposed if walking or cycling by the roadside and in high traffic conditions.[1]

Because Canadians spend close to 90% of their day indoors, exposure in indoor environments is an important consideration.[1,20] Factors that influence indoor gasoline engine exhaust concentrations include the air exchange rate in the building and whether it has an attached garage.[1] Greater rates of air exchange mean there is a greater influx of air from the outdoors, which leads to greater contributions of outdoor sources to indoor environments.[1] Having an attached garage can lead to increased exposure since contaminants can more readily enter the house.[21] For example, in Canada, benzene levels are three times higher in homes with attached garages compared to those with detached or no garages. The presence of benzene is attributable to engine exhaust, as well as to the evaporation of benzene from gasoline.[21]

Lastly, time spent in vehicles contributes a large proportion of total exposure to gasoline engine exhaust in adults.[22] Higher emissions are reported on arterial roads, where there is constant stopping and acceleration due to traffic lights. This is because fast acceleration increases the amount of exhaust produced.[22]

Occupational Exposures Overview

Inhalation is the primary route of occupational exposure to gasoline engine exhaust.[1]

CAREX Canada estimates that approximately 1.5 million Canadians are exposed to gasoline engine exhaust in their workplace. The largest industrial groups exposed include freight trucking, local, municipal and regional public administration, and offices of real estate agents and brokers​. Occupations at risk of gasoline engine exhaust exposure include transport truck drivers, delivery and courier service drivers, bus drivers, subway operators and other transit operators, and real estate agents and salespersons.

For more information, see the occupational exposure estimate for gasoline engine exhaust.


Photo: Wikimedia Commons, Ruben de Rijcke

1. International Agency for Research on Cancer (IARC). Monograph, Vol. 105. Diesel and Gasoline Engine Exhausts and some Nitroarenes (2014)
2. International Agency for Research on Cancer (IARC). Carcinogenicity of diesel-engine and gasoline-engine exhausts and some nitroarenes. The Lancet Oncol 2012;13(7), 663-664
3. Health Canada. Fuels and Air Pollution (2013)
4. International Programme on Chemical Safety (IPCS) INCHEM. Environmental Health Criteria 171, Diesel Fuel and Exhaust Emissions (1996)
6. Health Canada. Road Traffic and Air Pollution (2011) (PDF)
7. The Canadian Legal Information Institute (CanLII). Canadian Legal Information Institute website
8. The Canadian Legal Information Institute (CanLII). Benzene in Gasoline Regulations (SOR/97-493) (1997)
9. The Canadian Legal Information Institute (CanLII). Contaminated Fuel Regulations (SOR/91-486) (1991)
10. The Canadian Legal Information Institute (CanLII). Gasoline Regulations (SOR/90-247) (1989)
14. The Canadian Legal Information Institute (CanLII). Sulphur in Gasoline Regulations (SOR/99-236) (1998)
15. Natural Resources Canada. Demand and Consumption (2012)
17. Ministry of Justice. Health and the Environment: Critical Pathways (2002) (PDF)
18. Karner AA, Esinger DS, Niemeier DA. “Near-roadway air quality: synthesizing the findings from real-world data.” Environ Sci and Technol 2010;44:5534-5344. DOI: 10.1021/es100008x
20. Health Canada. Indoor Air Quality (2015)

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